main(List<String> args) {
  // 1.定义字符串
  var str1 = 'abc';
  var str2 = 'abc';
  var str3 = """
     abc
     def
     ghj
     """;

  //  2.字符串和表达式拼接
  var name = 'dart';
  var age = 19;
  var height = 1.8;
  // 强调：${变量},那么{}可以省略
  var message = "my name is ${name},age is ${age},height is ${height}";
  var message2 = "my name is ${name},type is ${name.runtimeType}";
  var message3 = "my name is $name,type is ${name.runtimeType}";
  print(message);
  print(message2);
  print(message3);
}
